Method and arrangement for compensating memory effects in power amplifier

Abstract

A method for compensating memory effects in a power amplifier comprises obtaining of an original signal. A variation of power of the original signal with time is determined. The original signal is predistorted for memory effects of the power amplifier into a predistorted signal. The predistorting comprises predistorting of the original signal in dependence of the variation of power. A power amplifier predistortion arrangement for compensating memory effects in a power amplifier, a power amplifier arrangement, and radio transmitter are also disclosed.

1 . A method for compensating memory effects in a power amplifier comprising:
 obtaining an original signal; and   predistorting said original signal for memory effects of said power amplifier into a predistorted signal by   determining a variation of power of said original signal with time,   wherein the predistorting comprises predistorting said original signal in dependence of said variation of power to generate a predistorted signal y(t).   
     
     
         2 . The method according to  claim 1 , further comprising:
 amplifying said predistorted signal into an amplified output signal.   
     
     
         3 . The method according to  claim 1 , wherein said variation of power of said original signal with time is a power measure difference between consecutive time slots. 
     
     
         4 . The method according to  claim 3 , wherein said power measure difference is a difference of instantaneous signal power. 
     
     
         5 . The method according to  claim 3 , wherein said power measure difference is a difference of average signal power, said average signal power being determined over a predetermined period of time. 
     
     
         6 . The method according to  claim 1 , wherein said predistorted signal y(t) is determined as:
     y ( t )=α 0   X   0 ( t )+α 3 δ 3 ( t ) X   3 ( t ),
   where X k (t), k=0, 3, is a vector of a power amplifier behavioural model structure α k , k=0, 3, are corresponding coefficients of said power amplifier behavioural model structure and δ 3  is a dependency factor being dependent on said variation of power of said original signal.   
     
     
         7 . The method according to  claim 1  further comprising:
 determining an additional memory effect dependency factor from said original signal, 
 wherein the predistorting comprises predistorting said original signal in further dependence of said additional memory effect dependency factor. 
 
     
     
         8 . The method according to  claim 1 , wherein said predistorted signal y(t) is determined as:
     y ( t )=α 0   X   0 ( t )+Σ k=1   K α k Π m=1   M(k) δ m,k ( t ) X   k ( t ),
   where X k (t), k=0, K, is a vector of a power amplifier behavioural model structure α k , k=0, K, are corresponding coefficients of said power amplifier behavioural model structure and δ m,k  are dependency factors, of which one is dependent on said variation of power of said original signal.   
     
     
         9 . The method according to  claim 1  further comprising:
 determining a mean power over a predetermined period of time of said original signal and a frequency of said original signal, 
 wherein the predistorting comprises predistorting said original signal in further dependence of said mean power and of said frequency. 
 
     
     
         10 . The method according to  claim 9 , wherein said predistorted signal y(t) is determined as:
     y ( t )=α 0   X   0 ( t )+α 1 δ 1 ( t ) X   1 ( t )+α 2 δ 2 ( t ) X   2 ( t )+α 3 δ 3 ( t ) X   3 ( t ),
   where X k (t), k=0, 1, 2, 3, is a vector of a power amplifier behavioural model structure α k , k=0, 1, 2, 3, are corresponding coefficients of said power amplifier behavioural model structure, δ 1  is a dependency factor being dependent on said mean power of said original signal, δ 2  is a dependency factor being dependent on said frequency of said original signal and δ 3  is a dependency factor being dependent on said variation of power of said original signal.   
     
     
         11 . The method according to  claim 9 , wherein said predistorted signal, y(t) is determined as:
     y ( t )=α 0   X   0 ( t )+α 1 δ 1 ( t )δ 2 ( t ) X   1 ( t )+α 3 δ 3 ( t ) X   3 ( t ),
   where X k (t), k=0, 1, 3, is a vector of a power amplifier behavioural model structure α k , k=0, 1, 3, are corresponding coefficients of said power amplifier behavioural model structure, δ 1  is a dependency factor being dependent on said mean power of said original signal, δ 2  is a dependency factor being dependent on said frequency of said original signal and δ 3  is a dependency factor being dependent on said variation of power of said original signal.   
     
     
         12 . A power amplifier predistorter for compensating memory effects in a power amplifier, comprising:
 a processor; and   a memory containing instructions which, when executed by the processor, cause the power amplifier predistorter to:
 obtain an original signal; and 
 predistort said original signal for memory effects of said power amplifier into a predistorted signal, by performing operations 
 to determine a variation of power of said original signal with time and 
 predistort said original signal in dependence of said variation of power to generate a predistorted signal. 
   
     
     
         13 . (canceled) 
     
     
         14 . The power amplifier predistorter of  claim 12 , wherein the power amplifier predistorter is coupled to a power amplifier and
 wherein said power amplifier is configured to amplify said predistorted signal into an amplified output signal.   
     
     
         15 . The power amplifier predistorter of  claim 14 , wherein the power amplifier is coupled to
 an antenna configured to transmit a radio signal according to said amplified output signal.   
     
     
         16 . A non-transitory computer-readable storage medium comprising instructions which, when executed by at least one processor, cause a predistorter for compensating memory effects in a power amplifier to perform operations comprising:
 obtaining an original signal; and
 predistorting said original signal for memory effects of a power amplifier into a predistorted signal by determining a variation of power of said original signal with time and predistorting said original signal in dependence of said variation of power to generate a predistorted signal. 
   
     
     
         17 - 20 . (canceled)